1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #pragma once 30 31 #include <stdlib.h> 32 #include <limits.h> 33 34 #include <android-base/macros.h> 35 36 static constexpr size_t kBlockSizeAlign = sizeof(void*); 37 static constexpr size_t kBlockSizeMin = sizeof(void*) * 2; 38 39 struct LinkerBlockAllocatorPage; 40 41 /* 42 * This class is a non-template version of the LinkerTypeAllocator 43 * It keeps code inside .cpp file by keeping the interface 44 * template-free. 45 * 46 * Please use LinkerTypeAllocator<type> where possible (everywhere). 47 */ 48 class LinkerBlockAllocator { 49 public: 50 explicit LinkerBlockAllocator(size_t block_size); 51 52 void* alloc(); 53 void free(void* block); 54 void protect_all(int prot); 55 56 // Purge all pages if all previously allocated blocks have been freed. 57 void purge(); 58 59 private: 60 void create_new_page(); 61 LinkerBlockAllocatorPage* find_page(void* block); 62 63 size_t block_size_; 64 LinkerBlockAllocatorPage* page_list_; 65 void* free_block_list_; 66 size_t allocated_; 67 68 DISALLOW_COPY_AND_ASSIGN(LinkerBlockAllocator); 69 }; 70 71 /* 72 * A simple allocator for the dynamic linker. An allocator allocates instances 73 * of a single fixed-size type. Allocations are backed by page-sized private 74 * anonymous mmaps. 75 * 76 * The differences between this allocator and BionicAllocator are: 77 * 1. This allocator manages space more efficiently. BionicAllocator operates in 78 * power-of-two sized blocks up to 1k, when this implementation splits the 79 * page to aligned size of structure; For example for structures with size 80 * 513 this allocator will use 516 (520 for lp64) bytes of data where 81 * generalized implementation is going to use 1024 sized blocks. 82 * 83 * 2. This allocator does not munmap allocated memory, where BionicAllocator does. 84 * 85 * 3. This allocator provides mprotect services to the user, where BionicAllocator 86 * always treats its memory as READ|WRITE. 87 */ 88 template<typename T> 89 class LinkerTypeAllocator { 90 public: LinkerTypeAllocator()91 LinkerTypeAllocator() : block_allocator_(sizeof(T)) {} alloc()92 T* alloc() { return reinterpret_cast<T*>(block_allocator_.alloc()); } free(T * t)93 void free(T* t) { block_allocator_.free(t); } protect_all(int prot)94 void protect_all(int prot) { block_allocator_.protect_all(prot); } 95 private: 96 LinkerBlockAllocator block_allocator_; 97 DISALLOW_COPY_AND_ASSIGN(LinkerTypeAllocator); 98 }; 99